- From: Michael Kifer <kifer@cs.sunysb.edu>
- Date: Tue, 24 Jul 2007 07:14:11 -0400
- To: Chris Welty <cawelty@gmail.com>
- Cc: "Boley, Harold" <Harold.Boley@nrc-cnrc.gc.ca>, "Public-Rif-Wg (E-mail)" <public-rif-wg@w3.org>
> >> * It seems to me a cleaner syntax is to remove existentials from > >> conditions and unify all quantifiers outside the rule (as with > >> universal now), and add a restriction in horn that existentially > >> quantified vars cannot appear in the conclusion. > > > > The RIF Basic Condition Language is meant to be reusable also > > (in PR and) outside the context of any rule, stand-alone (e.g. > > for queries and integrity checking), where existentials cannot > > be rewritten as universals in the Example 3b.->3a. manner. > > Oh, you misunderstood - I did not mean eliminate existentials from the > syntax entirely, I meant move them outside conditions into some sort > of wrapper or context (like, rules). This would make, at least, the > rule syntax cleaner. Unless I misunderstood you, what you are proposing is not sound in FOL: Exists X foo <- bar(X) is not the same as foo <- Exists X bar(X). --michael
Received on Tuesday, 24 July 2007 11:14:17 UTC